Note - Once again we are proud to be first to present more of Dr. Lee's frontline
research and information regarding the SARS epidemic and its dynamics. He deserves
worldwide recognition for his numerous personal contributions and citations
of other key data and information as below. - ed

Domestic houseflies (Musca domestica Linnaeaus) were examined for their ability
to harbor and transmit turkey coronavirus (TCV). Laboratory-reared flies were
experimentally exposed to TCV by allowing flies to imbibe an inoculum comprised
of turkey embryo-propagated virus (NC95 strain). TCV was detected in dissected
crops from exposed flies for up to 9 hr postexposure; no virus was detected
in crops of sham-exposed flies. TCV was not detected in dissected intestinal
tissues collected from exposed or sham-exposed flies at any time postexposure.
The potential of the housefly to directly transmit TCV to live turkey poults
was examined by placing 7-day-old turkey poults in contact with TCV-exposed
houseflies 3 hr after flies consumed TCV inoculum. TCV infection was detected
in turkeys placed in contact with TCV-exposed flies at densities as low as one
fly/bird (TCV antigens detected at 3 days post fly contact in tissues of 3/12
turkeys); however, increased rates of infection were observed with higher fly
densities (TCV antigens detected in 9/12 turkeys after contact with 10 flies/bird).
This study demonstrates the potential of the housefly to serve as a mechanical
vector of TCV. PMID: 12713170

Transmissible gastroenteritis (TGE) virus was detected in house flies (Musca
domestica Linneaus) by staining with specific fluorescent antibody. The flies
were collected within a swine confinement facility in which TGE was enzootic.
Laboratory-reared flies were infected experimentally with TGE virus and the
virus was recovered from the insects for 72 hours after infection. The TGE virus
was identified both by the fluorescent antibody technique and by isolation in
cell culture. The nature of plaque formation in cell monolayers inoculated with
the virus passaged through flies changed from a large plaque (4 mm or greater
in diameter) to a small plaque (1 mm in diameter) over the period. Large plaques
were observed early after infection and were attributed to TGE virus mechanically
carried by the flies. Small plaques occurred 8 to 12 hours after infection and
were considered to be produced by virus replicated in the dipterous cell. PMID:
6316821

So, Jeff, it is my reasonable guess that SARS coronavirus can be spread by house
flies for between 3 and 72 hours after a fly has come into contact with SARS
coronavirus as is likely to happen if a fly lands on any infected human waste/body
fluids. You will note that, for turkey coronavirus, it is sufficient to have
one single infected fly land on a bird and the bird can become infected. It
is a reasonable infection-control policy, as summer approaches and flies begin
flying, for any infected nation to institute fly abatement programs immediately
and for individual citizens of infected nations to be concerned about and proactive
about preventing contact with flies.

This is going to be a challenging summer in Asia. As flies (and perhaps other
insects?) are likely to spread the disease in the summer and the virus appears
to spread by close human contact in the winter and summer it is not likely that
SARS coronavirus will display any seasonality. Once flies begin flying, I anticipate
there will be an increase in SARS cases particularly in areas where flies have
access to human waste/body fluids and subsequent access to humans.

This is a really troublesome finding and does not bode well for quarantine effectiveness.
How does a nation protect itself from flies?